How can I solve my external hard drive problem?

I bought my second Samsung G3 external 2tb hard drive, I used it a few weeks ago to back up all my data on it and had no problems.
Since last week I am trying to use it but my computer will not pick it up and the lights shows that it’s on but it’s not on my system. I changed the ports a few times, rebooted my system a few times and even changed and checked the cables. I even tried to do a hardware search but still nothing. My other Samsung is working without any problems.